The invention relates generally to a drafting arrangement for a spinning machine and, more particularly, to such a drafting arrangement comprising at least one pair of feed rollers, one pair of central rollers and a pair of withdrawal rollers, wherein each roller pair comprising an upper roller and a lower roller with the lower rollers of the drafting arrangement being configured as roller segments, which are rotated by single-motor drives, and the upper rollers being mounted in a pendulum carrier.
In conjunction with spinning machines, for example with ring spinning machines or air spinning machines, drafting arrangements are known in various embodiments. The drafting arrangements differ here, sometimes substantially, for example, with regard to the number of their pairs of rollers, with respect to the structural design of their pendulum carriers or else with regard to the configuration of their lower rollers.
In particular in conjunction with ring spinning machines, drafting arrangements with lower rollers along the length of the machine are very widespread, for example. These lower rollers along the length of the machine are generally driven by a strong drafting arrangement motor which is arranged at the end of the machine in the drive frame of the textile machine and which ensures, via an interposed reduction gear, that the feed, central and withdrawal lower rollers rotate at different speeds and draw the presented fiber band (e.g., a sliver) in the process.
Such lower rollers along the length of the machine have a series of disadvantages, however. It is not only the bearing holding of such long lower rollers which is often rather difficult, changing the drawing conditions of the drafting arrangements generally also entails substantial outlay. Such long lower rollers are also subjected to high torsional stresses during the spinning operation and are inclined to distortions, which has a very negative effect on the quality of the drawing that is adjusted.
As in these lower rollers the assembly or replacement of the drawing belts, which are preferably arranged in the region of the central lower roller and are subjected to relatively high wear, is very expensive, various proposals have already been made in the past, as to how such long lower rollers can be replaced or modified in such a way that the aforementioned disadvantages do not occur.
To avoid high torsional stresses in long lower rollers, it has been proposed, for example, in German Patent Publication DE 100 40 420 A1, to either drive each of these lower rollers along the length of the machine by a plurality of accordingly weaker motors or to divide the lower rollers into a plurality of lower roller sections which can be driven individually. According to an embodiment shown in German Patent Publication DE 100 40 420 A1, arranged distributed over the entire length of a lower roller along the length of a machine are, for example, two or three motors, which together drive the lower roller. In the case of divided lower rollers, an individual separate drive is provided for each of the individual lower roller sections.
Although the devices described in German Patent Publication DE 100 40 420 A1 succeed in keeping the torsional stresses in the lower rollers within reasonable limits, in particular in the case of very long ring spinning machines, the other disadvantages of lower rollers of this type, in particular with regard to the assembly outlay during installation or when changing the drawing belts arranged in the region of the central lower rollers, could not be eliminated, however, with these devices.
A ring spinning machine is described in German Patent Publication DE 39 41 823 C1, which, instead of lower rollers along the length of the machine, in each case has a large number of relatively short lower roller sections which are driven by a single motor and, in conjunction with corresponding upper rollers, form the drafting arrangements. The lower roller sections are configured here as external rotor drives. In other words, a bearing axle is fixed so as to be rotationally engaged between two cheeks of the machine frame of the ring spinning machine and carries the stator of the external rotor drive. The electric rotor of the drive is arranged inside a rotatable hollow roller, which is also supported via corresponding bearing points on the bearing axle. The associated upper rollers, which are entrained by frictional engagement during the spinning operation of the lower roller section, rest on the hollow roller, which in each case forms a lower roller section for a plurality of spinning station drafting arrangements arranged next to one another.
German Patent Publication DE 39 41 823 A1 does not contain any more detailed indications, however, as to how the bearing points are formed in the cheeks of the ring spinning machine. In other words, it is not described anywhere in this patent whether the bearing axles are arranged so as to be stationary or replaceable, for example.
Drafting arrangements for spinning machines, which in each case have lower roller segments which can be driven by a single motor, are also known from German Patent Publication DE 39 32 614 A1.
In these known drafting arrangements, the individual drives of the lower roller segments are connected to a control device, which, via a corresponding inverter, can adjust the speed of the drives and therefore the drawing of the drafting arrangement. The lower roller segments are either connected here via a motor shaft directly to one of the drives or connected in each case to one of the drives via a drive belt.
It is also not shown or described in German Patent Publication DE 39 32 614 A1 how a bearing arrangement could appear in order to arrange lower roller drives, which are connected directly to a lower roller segment via their motor shaft, so as to be easily replaceable, in the machine frame of a textile machine, for example to change the drawing belts. In this patent, a bearing arrangement is merely described with the aid of an embodiment, in which the lower roller segments are connected to the drives via drive belts In this case, both the lower roller segments and the drives are displaceably mounted in longitudinal guides via special bearing parts such that the spacing between the roller segments can be adjusted and changed if necessary. To disassemble the lower roller segments and/or the drives, the respective longitudinal guides firstly have to be laboriously unscrewed from one another.